The Society for Leukocyte Biology (SLB) annual meeting from October 21-23, 2004 will be devoted to host-pathogen interactions on the cellular level. This important subject is at the interface between microbiology and cell biology, and the two disciplines are converging in this scientific arena. The recognition of microbes by host cells and the mechanisms employed by pathogens to escape from host defenses are two aspects of pathogenesis that are revolutionizing biology. SLB is made up primarily of cell biologists who focus on antigen presenting cells and the effector cells of innate immunity. In this meeting we aim to provide the latest information about how host cells combat infection and how microbial pathogens subvert these responses. David Russell and Brett Finlay, who are among the leading investigators in bacterial pathogenesis, have agreed to give the plenary talks, and the other invited speakers have made important contributions to our knowledge of antimicrobial host defenses. There will be 28 invited speakers (27 have been confirmed) and an additional 16 speakers will be selected, by a committee, from the abstracts that are submitted. The topics to be covered are mechanisms of phagocytosis and genetic defects in host cells that are predisposed to infections, type III secretion systems in pathogenic bacteria, the effect of M. tuberculosis on intracellular organelles, and antimicrobial effector mechanisms in phagocytes. We expect 300-400 registrants, mostly active researchers from academics and industry. We expect to attract a large number of Canadian scientists and students because the meeting is in Toronto and we have invited several prominent Canadian scientists to speak, including one of the keynote speakers. The venue is a large hotel that is wheel-chair accessible. Six of the confirmed speakers are women, all leading investigators in field, and the meeting co-chair is a woman. We encourage students and other trainees to submit abstracts; the SLB gives awards for the best abstracts submitted by students. One of the main purposes of the meeting is to encourage young scientists.